Liquid-fuel pot burner

ABSTRACT

A pot burner, which in an undefined sloping position with rocking movements functions well, particularly in vehicles and vessels, because the vaporing surface of the fuel is defined and because the vapored fuel is well mixed with air in a first cage, which is enclosed by a second cage.

The invention relates to a pot burner for liquid fuel, comprising asingle pot having at the top a flame orifice, the passage area of whichis smaller than the passage area for fuel vapours in the pot, a jacketsurrounding the pot, means for the supply of liquid fuel and means forthe supply of primary and secondary air.

A pot burner of this type is used in general for heating small rooms.During operation liquid fuel is conveyed from a level-control through asupply duct to the pot bottom. The liquid fuel supplied is uniformlyspread across the substantially horizontal pot bottom and gasified bythe high temperature of the surface of the pot bottom. However, if sucha pot burner is employed as a heating device for spaces in a vehicle ora vessel, the horizontal position of the pot bottom is not at allensured due to rocking movements or to an inclined position of thevehicle or the vessel. In this case the distribution of the suppliedliquid fuel across the pot bottom will not be uniform in different,desired control-positions of the level-control, which is inconvenient inthat the gasification process is not satisfactorily performed, the flamebecomes unsteady and the efficiency of the combustion is not at theoptimum as a result of which soot is produced and the CO-contents of thecombustion gases is high.

The invention has for its object to provide a pot burner of the kind setforth above, which due to certain provisions, is particularly suitablefor use as a space heating device in vehicles, vessels or other objectssubjected to rocking movements. A further object of the invention is toprovide a very simple construction of the pot burner so that itsmanufacture can take place at low cost.

The pot burner according to the invention is characterized by a ringarranged concentrically with the pot wall and connected with the potbottom for limiting the surface of the pot bottom to be wetted by liquidfuel, by an orifice arranged centrally in the pot bottom for the supplyof liquid fuel, by a first inverted cage snugly embracing the outersurface of said ring and having a closed top wall and an aperturedsidewall, by a second inverted cage arranged concentrically inside thefirst cage and having a closed top wall and an apertured sidewall, thelower side of which extends inside the space confined by the ring andthe pot bottom without contacting the surface of the ring and the potbottom, the distance between the lower edge of the sidewall of thesecond cage and the pot bottom being such as to ensure that under alloperational conditions of the pot burner the gasification is maintainedirrespective of deviations of the central axis of the pot burner fromthe vertical position occurring within given limits.

The invention will now be described more fully with reference to thefollowing figures:

FIG. 1 is a diagrammatic, vertical sectional view of one embodiment of apot burner constructed in accordance with the invention,

FIG. 2 is an exploded view of part of the sidewall of the first invertedcage,

FIG. 3 is an exploded view of part of the sidewall of the second,inverted cage, and

FIG. 4 is a variant of a pot burner shown in FIG. 1.

As shown in FIG. 1, the pot of the burner comprises a cylindricalsidewall 1, a bottom 2, and a top wall 3 having a recess giving accessto a flame orifice 4. The flame orifice 4 is bounded by an axiallyextending wall 5, which is at right angles to the top wall 3 of the pot.

The pot is surrounded by a jacket 6, which joins the top edge of thewall 5 of the flame orifice extending as far as beyond the pot bottom 2and has, on the bottom side, an orifice 7 for the inlet of air forced inby means of a fan (not shown). The air sucked in is driven upwards inthe space between the pot wall and the jacket and subsequently conductedaway through apertures 8 dispersed along the height of the pot wall intothe pot as primary air and respectively conducted away through apertures9 in the wall 5 of the flame orifice 4 as secondary air.

In a conventional manner a duct 10 connected with a level-control (notshown) is provided for the supply of liquid fuel. The duct 10 is passedacross the jacket 6 and opens into an opening 11 arranged centrally inthe pot bottom 2.

Concentrically provided inside the pot is a ring 12 of, for example,sheet steel which is connected with the bottom 2. The ring 12 limits thesurface of the pot bottom to be wetted by the liquid fuel andconcentrates the gasification process inside the space enclosed by thering. The outer surface of the ring 12 is snugly embraced by an invertedcage 13 having a closed top wall and a perforated side wall. Arrangedconcentrically inside the cage 13 is a second, inverted cage 14, theheight of which is equal to about half the height of the cage 13. Thesecond cage also has a top wall and a perforated sidewall. The cage 14is held in place by giving supporting means (not shown) in a manner suchthat the lower side of the sidewall extending inside the space confinedby the ring and the pot bottom without being in contact with the surfaceof he ring 12 and the pot bottom 2. The distance between the lower edgeof the side wall of the second cage 14 and the pot bottom is such thatunder all operational conditions of the pot burner the gasification ismaintained irrespective of deviations of the central axis 15 of the potburner from the vertical position occurring within given limits.

The two cages 13 and 14 are made from refractory material, particularlysheet steel, FIGS. 2 and 3 are exploded views of part of the sidewall ofthe first cage 13 and part of the sidewall of the second cage 14,respectively. From FIG. 2 it will be apparent that the first cage 13 hasnear the lower side a row of apertures 16 of a first type, saidapertures being substantially rectangular, above which a plurality ofrows of apertures 17 of a second type are provided, which aresubstantially circular. The passage area of each aperture 16 of thefirst type is larger than that of each aperture 17 of the second type.When the first cage 13 is disposed around the ring 12, the rectangularapertures 16 are bounded on the one hand by the top edge of the ring,whilst said apertures extend in the sidewall of the first cage along aheight which is smaller than the distance beween the top wall of theenclosed second cage 14 and the pot bottom 2. The comparatively large,rectangular apertures 16 serve to admit the combustion air unhinderedinto the second cage 14. The comparatively small apertures 18 of thesecond cage 14 are distributed throughout the entire sidewall thereof.

During operation the liquid fuel admitted is gasified on the part of thepot bottom inside the ring 12. Owing to the closed top walls of the twocages 13 and 14 the gas is driven sideways in order to raise thetemperature of the cages to an optimum value. The freely arranged cage14 attains a temperature (about 700° C.) which is appreciably higherthan the temperature (about 380° C.) of the pot bottom 2. The hotinternal cage 14 serves to maintain the gasification, even if the potburner is exposed to rocking movements within given limits, that is tosay even when the pot bottom moves out of its horizontal position, anddue thereto the contact surface between the distributed liquid fuel andthe pot bottom is reduced and the liquid fuel tends to flow through therectangular apertures 16 across the upper edge of the ring 12. Thecombustion air admitted through the comparatively large apertures 16 inthe external cage 13 into the internal cage 14 generates small flames onthe sidewalls of the two cages at the comparatively small apertures.These flames are maintained on the sidewall of the internal cage 14 bythe external cage 13 when the pot burner burns at higher capacity.

It has been found that diesel oil as a liquid fuel provides optimumresults and that even in the case of rocking movements within givenlimits the pot burner shows a quiet flame shape and ensures completecombustion in all positions of the level regulator.

It will be obvious that within the scope of the invention variousembodiments of the pot burner described above can be designed. The potburner may, for example, have an oval shape rather than a cylindricalone.

The pot burner illustrated in FIG. 4 differs from the one shown in FIGS.1-3 in that to increase the capacity of the pot burner a circular row ofadditional air apertures 20 is provided in the upper side of the jacket6, whereas a cover or screen 21 is arranged there above, said coverhaving a central orifice 22, the passage of which is considerablysmaller than that of the flame orifice 4.

FIG. 4 also shows that the cage 14 is suspended from the cage 13 by acentral rod 23, the orifice 7 is connected by an air duct 24 to a blower25 and the duct 10 receives fuel from a storage tank 26 through a floatdevice 27, in which the liquid level 28 is maintained by means of afloat 29 controlling a valve 30. The difference a in levels between theliquid level 28 and the pot bottom 2 is for instance 20 mm. The adjustedquantity of fuel is, at this difference in levels, controlled by acontrol valve 31 which influences the flow resistances of the fuel.

I claim:
 1. A pot burner for liquid fuel, comprising a pot having a top,a depending pot wall and a pot bottom, said top including a flameorifice defining a top passage area which is smaller than the potpassage area for fuel vapours in the pot, a jacket surrounding the pot,means for the supply of primary and secondary air to said pot passagearea, a ring arranged concentrically with the pot wall and connectedwith the pot bottom for limiting the surface of the pot bottom to bewetted by liquid fuel, an orifice arranged centrally in the pot bottomfor the supply of liquid fuel, a first cage fixed to and adjoining thering and having an apertured sidewall, a second cage arrangedconcentrically inside the first cage and having a closed, imperforatetop wall and an apertured sidewall, the lower side of said second cageextending inside the space defined by the ring and the pot bottom, thefirst cage extending to a higher level than the second cage, the firstcage having a closed, imperforate top wall, and the second cage beingspaced from and arranged without being in contact with the surface ofthe ring and the pot bottom.
 2. A pot burner as claimed in claim 1,wherein the sidewall of the first cage has a height which is about twicethat of the second cage and has a row of apertures of a first type nearthe lower side and a plurality of rows of apertures of a second typelocated above the former, the passage area of each aperture of the firsttype being larger than that of each aperture of the second type.
 3. Apot burner as claimed in claim 2, wherein the apertures of the firsttype of the first cage are substantially rectangular, are bounded on theone hand by the top edge of the ring and extend in the sidewall of thefirst cage along a height which is smaller than the distance between thetop wall of the enclosed second cage and the pot bottom.
 4. A pot burneras claimed in claim 1, 2 or 3 wherein the apertures of the second cageare provided throughout the entire sidewall thereof.
 5. A pot burner asclaimed in claim 1, 2, or 3 wherein a cover is arranged above the flameorifice, said cover having a central opening above the flame orifice,which central opening has a considerably smaller passage area than theflame orifice, and additional air apertures are provided for the supplyof additional air to the space contained beneath the cover.
 6. A potburner as claimed in claim 4 wherein a cover is arranged above the flameorifice, said cover having a central opening above the flame orifice,which central opening has a considerably smaller passage area than theflame orifice, and additional air apertures are provided for the supplyof additional air to the space contained beneath the cover.
 7. A potburner for liquid fuel comprising, in combination:a pot having a bottomwall and an upstanding perforate side wall; means upstanding from asmall central portion of said bottom wall for defining a fuel bowl andinlet means for supplying liquid fuel to said fuel bowl; a jacket havinga side wall surrounding and spaced radially outwardly from saidperforate side wall of the pot to define an air chamber, said pot andsaid jacket defining a restricted flame orifice above said fuel bowl andincluding secondary air passage means communicating said flame orificewith said air chamber, said jacket having air inlet means for supplyingpressurized air to said air chamber whereby primary combustion air isforced to flow through said perforate side wall of the pot and secondarycombustion air is forced to flow through said secondary air passagemeans; and means for causing liquid fuel in said bowl to be gasified insaid bowl and comprising inner cage means for causing the liquid fuel togasify in said bowl and outer cage means for maintaining said inner cagemeans at a sufficiently high temperature as to assure said liquid fuelto gasify in said bowl, said inner cage means having a top wall and adepending, perforate side wall presenting a lower edge projecting intothe confines of said bowl in inwardly spaced relation thereto and beingspaced above said bottom wall of the pot, said outer cage means having atop wall spaced below said flame orifice and above the top wall of theinner cage means and a depending, perforate side wall surrounding atleast the upper portion of the side wall of said inner cage means, saidside wall of the pot and said means for causing liquid fuel in said bowlto be gasified in said bowl defining an inner air chamber into whichcombustion air flows through said perforate side wall of the pot fromsaid air chamber, the top walls of said inner and outer cage means beingimperforate whereby gasified fuel from said bowl is caused to flowradially outwardly through said perforate side walls of the inner andouter cage means essentially countercurrent to the flow of primarycombustion air whereby to generate small flames on said side walls ofthe inner and outer cage means at the perforations thereof, said outercage means presenting large primary air passage means to admit primarycombustion air essentially unhindered into said inner cage means.
 8. Apot burner for liquid fuel comprising, in combination:a pot having abottom wall and an upstanding perforate side wall; means upstanding froma small central portion of said bottom wall for defining a fuel bowl andinlet means for supplying liquid fuel to said fuel bowl; a jacket havinga side wall surrounding and spaced radially outwardly from saidperforate side wall of the pot to define an air chamber, said pot andsaid jacket defining a restricted flame orifice above said fuel bowl andincluding secondary air passage means communicating said flame orificewith said air chamber, said jacket having air inlet means for supplyingpressurized air to said air chamber whereby primary combustion air isforced to flow through said perforate side wall of the pot and secondarycombustion air is forced to flow through said secondary air passagemeans; and means for causing liquid fuel in said bowl to be gasified insaid bowl and comprising inner cage means for causing the liquid fuel togasify in said bowl and outer cage means for maintaining said inner cagemeans at a sufficiently high temperature as to assure said liquid fuelto gasify in said bowl, said inner cage means having a top wall and adepending, perforate side wall presenting a lower edge projecting intothe confines of said bowl in inwardly spaced relation thereto and beingspaced above said bottom wall of the pot, said outer cage means having atop wall spaced below said flame orifice and above the top wall of theinner cage means and a depending, perforate side wall surrounding atleast the upper portion of the side wall of said inner cage means, saidside wall of the pot and said means for causing liquid fuel in said bowlto be gasified in said bowl defining an inner air chamber into whichcombustion air flows through said perforate side wall of the pot fromsaid air chamber, the top walls of said inner and outer cage means beingimperforate.